I don't have any software for planning quilts, the math nerd in me loves figuring it all out with paper and pencil.
Graph or gridded paper can help you make a helpful "map" of your planned quilt. If you use each of the squares to represent one square inch on your quilt, it can be helpful to calculate the measurements of pieces, blocks, borders, etc. If you're making a bed quilt you may need to tape a few sheets of graph paper together to keep the 1 square = 1 inch proportion.
You could then scan your graphs and post the images here; you would get lots of help with the math.